On Mon, Aug 17, 2020 at 05:53:09PM -0400, Jim Quinlan wrote:
> The new field 'dma_range_map' in struct device is used to facilitate the
> use of single or multiple offsets between mapping regions of cpu addrs and
> dma addrs. It subsumes the role of "dev->dma_pfn_offset" which was only
> capable of holding a single uniform offset and had no region bounds
> checking.
>
> The function of_dma_get_range() has been modified so that it takes a single
> argument -- the device node -- and returns a map, NULL, or an error code.
> The map is an array that holds the information regarding the DMA regions.
> Each range entry contains the address offset, the cpu_start address, the
> dma_start address, and the size of the region.
>
> of_dma_configure() is the typical manner to set range offsets but there are
> a number of ad hoc assignments to "dev->dma_pfn_offset" in the kernel
> driver code. These cases now invoke the function
> dma_attach_offset_range(dev, cpu_addr, dma_addr, size).
...
> + if (dev) {
> + phys_addr_t paddr = PFN_PHYS(pfn);
> +
> + pfn -= (dma_offset_from_phys_addr(dev, paddr) >> PAGE_SHIFT);
PFN_DOWN() ?
> + }
...
> + pfn += (dma_offset_from_dma_addr(dev, addr) >> PAGE_SHIFT);
Ditto.
...
> +static inline u64 dma_offset_from_dma_addr(struct device *dev, dma_addr_t dma_addr)
> +{
> + const struct bus_dma_region *m = dev->dma_range_map;
> +
> + if (!m)
> + return 0;
> + for (; m->size; m++)
> + if (dma_addr >= m->dma_start && dma_addr - m->dma_start < m->size)
> + return m->offset;
> + return 0;
> +}
> +
> +static inline u64 dma_offset_from_phys_addr(struct device *dev, phys_addr_t paddr)
> +{
> + const struct bus_dma_region *m = dev->dma_range_map;
> +
> + if (!m)
> + return 0;
> + for (; m->size; m++)
> + if (paddr >= m->cpu_start && paddr - m->cpu_start < m->size)
> + return m->offset;
> + return 0;
> +}
Perhaps for these the form with one return 0 is easier to read
if (m) {
for (; m->size; m++)
if (paddr >= m->cpu_start && paddr - m->cpu_start < m->size)
return m->offset;
}
return 0;
?
...
> + if (mem->use_dev_dma_pfn_offset) {
> + u64 base_addr = (u64)mem->pfn_base << PAGE_SHIFT;
PFN_PHYS() ?
> +
> + return base_addr - dma_offset_from_phys_addr(dev, base_addr);
> + }
...
> + * It returns -ENOMEM if out of memory, 0 otherwise.
This doesn't describe cases dev->dma_range_map != NULL and offset == 0.
> +int dma_set_offset_range(struct device *dev, phys_addr_t cpu_start,
> + dma_addr_t dma_start, u64 size)
> +{
> + struct bus_dma_region *map;
> + u64 offset = (u64)cpu_start - (u64)dma_start;
> +
> + if (!offset)
> + return 0;
> +
> + if (dev->dma_range_map) {
> + dev_err(dev, "attempt to add DMA range to existing map\n");
> + return -EINVAL;
> + }
> +
> + map = kcalloc(2, sizeof(*map), GFP_KERNEL);
> + if (!map)
> + return -ENOMEM;
> + map[0].cpu_start = cpu_start;
> + map[0].dma_start = dma_start;
> + map[0].offset = offset;
> + map[0].size = size;
> + dev->dma_range_map = map;
> +
> + return 0;
> +}
...
> +void *dma_copy_dma_range_map(const struct bus_dma_region *map)
> +{
> + int num_ranges;
> + struct bus_dma_region *new_map;
> + const struct bus_dma_region *r = map;
> +
> + for (num_ranges = 0; r->size; num_ranges++)
> + r++;
> + new_map = kcalloc(num_ranges + 1, sizeof(*map), GFP_KERNEL);
> + if (new_map)
> + memcpy(new_map, map, sizeof(*map) * num_ranges);
Looks like krealloc() on the first glance...
> +
> + return new_map;
> +}
--
With Best Regards,
Andy Shevchenko
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